Merge pull request #32529 from marcingrzejszczak

* gh-32529:
  Polish "Prefer WebClient to RestTemplate for Zipkin's Sender"
  Prefer WebClient to RestTemplate for Zipkin's Sender

Closes gh-32529

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/tracing/zipkin/ZipkinConfigurations.java

@@ -28,7 +28,6 @@ import zipkin2.reporter.urlconnection.URLConnectionSender;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
-import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.boot.web.client.RestTemplateBuilder;
 import org.springframework.context.annotation.Bean;
@@ -46,8 +45,8 @@ import org.springframework.web.reactive.function.client.WebClient;
 class ZipkinConfigurations {
 
 	@Configuration(proxyBeanMethods = false)
-	@Import({ UrlConnectionSenderConfiguration.class, RestTemplateSenderConfiguration.class,
+	@Import({ UrlConnectionSenderConfiguration.class, WebClientSenderConfiguration.class,
-			WebClientSenderConfiguration.class })
+			RestTemplateSenderConfiguration.class })
 	static class SenderConfiguration {
 
 	}
@@ -85,7 +84,7 @@ class ZipkinConfigurations {
 	}
 
 	@Configuration(proxyBeanMethods = false)
-	@ConditionalOnWebApplication(type = ConditionalOnWebApplication.Type.REACTIVE)
+	@ConditionalOnClass(WebClient.class)
 	@EnableConfigurationProperties(ZipkinProperties.class)
 	static class WebClientSenderConfiguration {
 

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/tracing/zipkin/ZipkinConfigurationsSenderConfigurationTests.java

@@ -25,6 +25,7 @@ import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.test.context.FilteredClassLoader;
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
 import org.springframework.boot.test.context.runner.ReactiveWebApplicationContextRunner;
+import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
 import org.springframework.boot.web.client.RestTemplateBuilder;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -46,6 +47,9 @@ class ZipkinConfigurationsSenderConfigurationTests {
 	private final ReactiveWebApplicationContextRunner reactiveContextRunner = new ReactiveWebApplicationContextRunner()
 			.withConfiguration(AutoConfigurations.of(SenderConfiguration.class));
 
+	private final WebApplicationContextRunner servletContextRunner = new WebApplicationContextRunner()
+			.withConfiguration(AutoConfigurations.of(SenderConfiguration.class));
+
 	@Test
 	void shouldSupplyBeans() {
 		this.contextRunner.run((context) -> {
@@ -56,8 +60,8 @@ class ZipkinConfigurationsSenderConfigurationTests {
 	}
 
 	@Test
-	void shouldUseWebClientSenderIfWebApplicationIsReactive() {
+	void shouldPreferWebClientSenderIfWebApplicationIsReactiveAndUrlSenderIsNotAvailable() {
-		this.reactiveContextRunner.withUserConfiguration(WebClientConfiguration.class)
+		this.reactiveContextRunner.withUserConfiguration(RestTemplateConfiguration.class, WebClientConfiguration.class)
 				.withClassLoader(new FilteredClassLoader("zipkin2.reporter.urlconnection")).run((context) -> {
 					assertThat(context).doesNotHaveBean(URLConnectionSender.class);
 					assertThat(context).hasSingleBean(Sender.class);
@@ -65,6 +69,56 @@ class ZipkinConfigurationsSenderConfigurationTests {
 				});
 	}
 
+	@Test
+	void shouldPreferWebClientSenderIfWebApplicationIsServletAndUrlSenderIsNotAvailable() {
+		this.servletContextRunner.withUserConfiguration(RestTemplateConfiguration.class, WebClientConfiguration.class)
+				.withClassLoader(new FilteredClassLoader("zipkin2.reporter.urlconnection")).run((context) -> {
+					assertThat(context).doesNotHaveBean(URLConnectionSender.class);
+					assertThat(context).hasSingleBean(Sender.class);
+					assertThat(context).hasSingleBean(ZipkinWebClientSender.class);
+				});
+	}
+
+	@Test
+	void shouldPreferWebClientInNonWebApplicationAndUrlConnectionSenderIsNotAvailable() {
+		this.contextRunner.withUserConfiguration(RestTemplateConfiguration.class, WebClientConfiguration.class)
+				.withClassLoader(new FilteredClassLoader("zipkin2.reporter.urlconnection")).run((context) -> {
+					assertThat(context).doesNotHaveBean(URLConnectionSender.class);
+					assertThat(context).hasSingleBean(Sender.class);
+					assertThat(context).hasSingleBean(ZipkinWebClientSender.class);
+				});
+	}
+
+	@Test
+	void willUseRestTemplateInNonWebApplicationIfUrlConnectionSenderIsNotAvailable() {
+		this.contextRunner.withUserConfiguration(RestTemplateConfiguration.class)
+				.withClassLoader(new FilteredClassLoader("zipkin2.reporter.urlconnection")).run((context) -> {
+					assertThat(context).doesNotHaveBean(URLConnectionSender.class);
+					assertThat(context).hasSingleBean(Sender.class);
+					assertThat(context).hasSingleBean(ZipkinRestTemplateSender.class);
+				});
+	}
+
+	@Test
+	void willUseRestTemplateInServletWebApplicationIfUrlConnectionSenderIsNotAvailable() {
+		this.servletContextRunner.withUserConfiguration(RestTemplateConfiguration.class)
+				.withClassLoader(new FilteredClassLoader("zipkin2.reporter.urlconnection")).run((context) -> {
+					assertThat(context).doesNotHaveBean(URLConnectionSender.class);
+					assertThat(context).hasSingleBean(Sender.class);
+					assertThat(context).hasSingleBean(ZipkinRestTemplateSender.class);
+				});
+	}
+
+	@Test
+	void willUseRestTemplateInReactiveWebApplicationIfUrlConnectionSenderIsNotAvailable() {
+		this.reactiveContextRunner.withUserConfiguration(RestTemplateConfiguration.class)
+				.withClassLoader(new FilteredClassLoader("zipkin2.reporter.urlconnection")).run((context) -> {
+					assertThat(context).doesNotHaveBean(URLConnectionSender.class);
+					assertThat(context).hasSingleBean(Sender.class);
+					assertThat(context).hasSingleBean(ZipkinRestTemplateSender.class);
+				});
+	}
+
 	@Test
 	void shouldNotUseWebClientSenderIfNoBuilderIsAvailable() {
 		this.reactiveContextRunner.run((context) -> {
@@ -74,16 +128,6 @@ class ZipkinConfigurationsSenderConfigurationTests {
 		});
 	}
 
-	@Test
-	void shouldUseRestTemplateSenderIfUrlConnectionSenderIsNotAvailableAndWebAppIsNotReactive() {
-		this.contextRunner.withUserConfiguration(RestTemplateConfiguration.class)
-				.withClassLoader(new FilteredClassLoader("zipkin2.reporter.urlconnection")).run((context) -> {
-					assertThat(context).doesNotHaveBean(URLConnectionSender.class);
-					assertThat(context).hasSingleBean(Sender.class);
-					assertThat(context).hasSingleBean(ZipkinRestTemplateSender.class);
-				});
-	}
-
 	@Test
 	void shouldBackOffOnCustomBeans() {
 		this.contextRunner.withUserConfiguration(CustomConfiguration.class).run((context) -> {